1. Field of the Invention
The invention relates to a process for renewing a refractory lining in a ladle and an apparatus for accomplishing the process.
2. Description of the Related Art
To an increasing extent nowadays, metallurgical vessels are no longer being lined (faced) with refractory bricks. Instead, a casting technique is used in which a refractory casting material, generally a thixotropically acting casting material, is introduced into the interspace between a template or mold which determines the desired clear interior space of the ladle or other type of metallurgical vessel and the vessel wall to be lined. Due to its thixotropic behavior, the material flows very well under the action of vibrations (generally of the template or mold), even in the case of low water contents, and fills every cavity.
German Offenlegungsschrift 3,741,073 has already disclosed a process in which, at the end of the life of a metallurgical vessel, that is to say after the inner layers of the casting material which have been exposed to the molten metal have worn away, instead of breaking out completely the remainder of the refractory lining, which is of course still serviceable, only the remaining slag residues and the slag-penetrated surface layers of the old lining are superficially removed. This does not involve the production of a geometrically regular surface but an operation in which a so-called slag-stripping robot with tools mounted on movable arms, rolling on the surface and having projecting sintered-carbide studs acts on the surface under the action of vibrations and removes or at least roughens it to the desired extent. During this operation, however, the tools follow the largely existing contour of the old lining. The template is reintroduced into the metallurgical vessel having the old lining cleaned in this way, and the interspace between the template and the old lining is then filled again with thixotropic casting material under the action of vibrations. In this way, it is possible to save up to 50% of the expensive lining material. The preceding machining of the surface of the old lining results in a good bond with the newly applied refractory material.
The known process, however, proves to be too expensive in certain cases. This is the case when the skull, i.e. the slag layer, is so thick that the time involved in removing it and the associated wear of the tools are too great to keep the process cost-effective. In addition, the remaining portion of the refractory lining is subjected to high mechanical stresses by the prolonged action of the tools and cracks can thus arise.